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Message-ID: <20240326065026.1910584-1-liushixin2@huawei.com>
Date: Tue, 26 Mar 2024 14:50:26 +0800
From: Liu Shixin <liushixin2@...wei.com>
To: Andrew Morton <akpm@...ux-foundation.org>
CC: Jan Kara <jack@...e.cz>, Matthew Wilcox <willy@...radead.org>, Alexander
Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>,
<linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-mm@...ck.org>, Liu Shixin <liushixin2@...wei.com>
Subject: [PATCH v3] mm/filemap: don't decrease mmap_miss when folio has workingset flag
If there are too many folios that are recently evicted in a file, then
they will probably continue to be evicted. In such situation, there is
no positive effect to read-ahead this file since it is only a waste of IO.
The mmap_miss is increased in do_sync_mmap_readahead() and decreased in
both do_async_mmap_readahead() and filemap_map_pages(). In order to skip
read-ahead in above scenario, the mmap_miss have to increased exceed
MMAP_LOTSAMISS. This can be done by stop decreased mmap_miss when folio
has workingset flag. The async path is not to care because in above
scenario, it's hard to run into the async path.
Signed-off-by: Liu Shixin <liushixin2@...wei.com>
Reviewed-by: Jan Kara <jack@...e.cz>
---
v2->v3: Update the title and comment. And add reviewed-by from Jan.
Andrew, please update patch[2] with this new patch, thanks.
mm/filemap.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index 8df4797c5287..780aad026b26 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3439,7 +3439,15 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf,
if (PageHWPoison(page + count))
goto skip;
- (*mmap_miss)++;
+ /*
+ * If there are too many folios that are recently evicted
+ * in a file, they will probably continue to be evicted.
+ * In such situation, read-ahead is only a waste of IO.
+ * Don't decrease mmap_miss in this scenario to make sure
+ * we can stop read-ahead.
+ */
+ if (!folio_test_workingset(folio))
+ (*mmap_miss)++;
/*
* NOTE: If there're PTE markers, we'll leave them to be
@@ -3488,7 +3496,9 @@ static vm_fault_t filemap_map_order0_folio(struct vm_fault *vmf,
if (PageHWPoison(page))
return ret;
- (*mmap_miss)++;
+ /* See comment of filemap_map_folio_range() */
+ if (!folio_test_workingset(folio))
+ (*mmap_miss)++;
/*
* NOTE: If there're PTE markers, we'll leave them to be
--
2.25.1
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